Method and apparatus for forming sheet metal



June 23, 1931. 1,811,259

METHOD AND APPARATUS Eon EOEMING SHEET METAL A. R. c uRTls 28, 1923 4 Sheets-Sheet l L ,Z

Filed Dec.

4 Sheets-Sheet 2 f 77'or A. R. CURTIS June 23, 193.1.

Filed Dec. 2B, .1.923

L 1| l lf//// 'I- l l|| l 'Il' ,June 23, 1931. ,1 R, CURHS 1,811,259

METHOD AND'APPARATS FOR FORMING SHEET METAL Filed Dec. 28, 1923 4 Sheets-Sheet 3 8 8 I6 'y 1b /0 6 i 1 "l 7 l 60 ,f /L/ f/ :if 5 LMI l G l O l /T/veno UWMW m June 2s, 1931. A.R.URT1S 1,811,259

METHOD AND APPARATUS FOR FORMING SHEET METAL Filed Dec. 28, 1923 4 Sheets-Sheet 4 Q/Zfw@ M1! VPatented June 23, 1931 PATENT i ortica Y i ,ARTHUR n.' configs, or 1omav-111LA1SI13, oHIo vi11rnzrnonannairnnnirns non nonnina4 SHEET METAL lnppneaaqn niea-neembeas, 192e. serial naesaaoe.

This' invention relatesftoa method and apparatus for forming sheetfmetal articlesand moreA vp articularly `to theV method-and. means for forming sharp bends Vacross vunweakenedj t areas-of sheets, such areas'lying between and adjacent to larger 4areas which have been greatly weakened by being perforated.

Aslshown herein, the invention is applied tothe formation ofthe cylindrical shell of 111 a washing machine cylinder in which the shell is Aprovided with integral reentrant portions form-ing baffles, they cylindrical portions of the" shell and thev sides ofthe baffles being providedwith closely adjacent perforations. `l5 Anch-ject ofthe invention fis to provide a methodY for bending. sheets which have Vperforated areas separated by relatively narrow unperforated strips'by operating upon `the uniperf'orated portions of thesheet to form fm'relatively sharp' bends therein without dis torting the perforated portions of the sheet. In forming `sharp or? fairly sharp bends in sheet'metal, a set must be given to veach-bendj by -t'he lapplication -ofa heavy force to the j 25 parts 'ma-king the ben'dat the end ofthe bending operation.V YIt islan object of the present invention `to provide means for effectively applying the necessary `pressure to the por-i tions ofthe lsheet at the bends'at' the ends'of the bend-ing operation. It is very desirable in awasher cylinder'that theholesin the perforated areas be indented, i. e. flanged out slightly and it is one ofthe main objects-of the present invention to provide a method 'uidandfapparatus forforining such'cylinders in which the perforated sheets "with indented openings may be givenV the desired' form without distorting, flattening or ironing out the A further object of the invention istoipro vide a 'method'and means yby which the integral yreentrant portions orlbaffles inthe shell j may bei formed one at a timey and yportions of the-'cylindrical partoflthelshell onopposite sides of Vthe baiies may be' simultaneously formed-so that after a numberfofoperations equalto the numberloffbalfles in the cylindri- 'al shell al complete cylindrical shell will be warmed. g f Y 1- f flanges or indentations surrounding the open* v l areas a which form the cylindrical portions 90 With the above and other objects in view, the invention may be said to comprise the method and apparatus as illustrated in the accompanying drawings described in the folv lowing specification and specifl'allyfset forth 5ft 1n the appended claims, together with Such variations and modifications thereof as will be apparent to one skilled `in the art to Which the invention appertains.

Reference shouldbe had to the accompany- 613i ing drawings :forming apart of this specification inrwhich Figure l is lan end ,elevation'of the forming apparatus, the parts being shown in the positionwhere the formingoperation 1s complete; Fig. f2 is a partialv vertical sec- Gi? tion on line 2-.--24 of Fig. l; Fig, 3 isla horizontal section at one end of the machine taken on line 3 3 Aof Fig. 1; Fig. 4 is a transverse section taken online 4 4 of Fig. 2 and showing thefposition of the forming parts 'mi when the sheet is introduced; Fig.V 5 is an end elevation showing the formingzparts in the position they occupy at the instant when the formation of the baffle is just beginning; Fig. 6 is a fragmentary plan view showing a partof'a perforated sheet from which the 'cylindrical shell isu to be formed; Fig. 't' shows the cylindrical shell vcompletely. formed; Fig. 8 is a fragmentary section shows ing a small portion of the sheet on an en- 59 larged scale, the section being taken through indented perforations. i f Referring first to Figs, 7 and8 of the drawings, the sheet from which the cylinder is to be formed is designated generally by the 85 letter S.' The completed cylinder is designated `generally bythe letter C and the integralbaflies are indicatedfby the letter B. Thesheet S has rrelatively large perforated of the cylindrical shell of the washer cylinder and a pair Aof narrow perforated areas lying between each pair of adjacent large perforated areas aand forming in thecompleted cylindrical shell the side walls of the 95 lloailies B. Between each of thelarge perforated areas a andthe adjacent narrow perforated area. Z) there is a narrow transversely extending unperforated strip c and between the adjacent narrow perforated areas bthere 3.90

'is a narrow unperforated strip CZ. kThe lines lof bend at the bases and Ypeaks of the baf- Y fles are formed-along the central portions of the narrow unperforated'strips c and ZQ The bend lines at the bases and peaks of the baffles being indicated in F ig. 6 at m and n. As shown in Fig. 8 4each yof theholes e in the sheet Silas a surrounding short flange or indentation f.

In accordance withv the present invention,

- the perforations are first formed in thesheet i ing members'which havea vpressure engage- S by any suitable means, such as a punch press and the cylindrical shell is then formed from'the perforated sheet Ssby successively;

forming portions of the sheet between formment with thesheet only along the'unperforated strips the' sheet being bent simulta-A neously along the bend lines n and m to form a `ribo'r baffle', the vmetal beinggiven a per-k manent set'at the end of thebending operationbyapplying arelatively heavy pressure 1 `tothe unperforatedstrips'adj acent the bends. The cylindrical portions of the shell on'opposite sides vof each vribor'baffle are formed simultaneously' betweenV forming members with cooperating cylindrical faces which are recessed rto' accommodate theV indentations surrounding the holes in the perforated areas and having pressure applyingedge portions which'engage the sheet only -alongfthe un-V Yperforatedstrips 0 and along'V the lunperforated edges g'of the sheet.` f f Referring tothe apparatus illustrated in Figs. 1 to v5 inclusive,the mechanism is sup# ported upon a suitableframe or. housingconsistingL ofy two end` standards 1 ywhich arejoined by the stationary form 1a whichhas an'upper ycylindrical Vforming face, the 'axis of which liesi'n thecentral longitudinal plane of the frame; The end .standards'of the frame have vertical guide Ybars floextending upwardly `ab'me' the fXedj form 1a whichserve as `guides for forming Ymembers which will be hereinafter described.JV

l tending longitudinallyzand,centrally thereofis a drive shaft 2 adapted to be driven 'from any suitable sourceof power'thr'oug'h a gearV 3 iixedrthereto; .Allof the'movable parts' l ofthe forming 'apparatus are operated from the drive shaft 2; On the upper face of the xedform la and'oentrally thereof therev is Vvan upwardly projectingvrib4 which corre-v `sponds in shape tothe baffle of the cylindri:l

l cal shellto be formed7 theflx'ed cylindricalI form la and baffle form 4 providing affixedv -form upon which a vportion of the sheet is lbent byL 'suitable movable forming members: into the' form of one of the re'entrant baffles and adjacent cylindrical portions offv the" v shell. 'A slidingfforming member 5 is mountedrlfor vertical. movement directly over the lixedgrib 4 andisadapted to be movedinto Vandoutof engagement with the peak of the rib 4, the Ysliding Vforrn 5 cooperating With the fixed rib 4 in forming the bend at Vthe peak l0f the reentrant bahe. In additionto the sliding form 5 there are a pair of bodily movable pivoted forming members 6 which have lower cylindrical faces 6a adapted to cooperate with thevfixedcylindrical form 1a and substantially` flat faces 6b. along their -inner sides which cooperate with the side faces ofthe, rib 4 in forming the sides of the bath-es." The forming members 6 are pivotal# ly'.V mounted upon a horizontal shaft 7 whose Y Vmost position, from the shaft 7 but-permitrelative bodily movement between the form 5 and'pivoted forming members 6 during the forming operation. `The pivoted' forming members6 are normally` held in spread position by flat springs 10 which. are secured at their' ends adjacent lthe outer lends :of the pivoted members 6 and pass over the 'topV of the shaft 7. The pivoted forms Gare guided in their movements towardv and from" the fixed form byv means of rollers 11 journaled onV pins 12 securedto opposite endsof the forms 6. The rollers V12 ,when the forming members 6 arey in their-y uppermostposition bear'against the 'inner faces of thev vertical guide bars/1b andengage other guide membersas t-he pivo-ted forms 6 approach the fixed form in the forming operation.' vVertical' movements 4of the pivotedforms 6 are con-I trolled byconnectingflinks 13 which connectthe opposite ends of the sliding V shaft 7 with crankpins 1 4 secured in crank `arms 15 which are keyedjtoY the'opposlite endsof the drive shaft- 2. The connectinglinks 131lie beyond.

the lendsofthe drive shaft 2 sothat during a rotation oftheshafuftheshaft; 7 and the forming members 6 carriedthereby are given A a fverticalreciprocating movement. The sliding formis provided `with' trunnions 5a on Vitsopposite ends from which are sus-VV pended hook linksl, the 'lower-hookedends of which engage Withhalf eccentrics 17 made;`

integralf-with the crank arms 155m the*v inner sides thereof. The eccentrics 17 serve to impartan additional movement to the slid:- ing forme lduring the final portion ofthe 'forming operation, ggMeans areprovided `to,

kvimpart* an inward swinging movement to the plvoted form 6 during the forming operation.

To this endguideibars or levers 18 are fulcrumedon pins 1,91securedinthemain frame and theselevers have cam faces 18d and 186 attheir upperf ends which are engaged bythe rollers 11 during the downward movement of the pivoted forming members causing the pivotedforming members 6to swing inwardly toward the opposite faces of the rib 4 of the fixed form during the forming operation.

For giving a final set to the bendsat thebase of the reentrant bao, meansy are provided to exert afdirect inward pressure upon'the rollers l1V toforce the forming faces 6b of tlie.;pivoted member 6 against the opposite side faces of therib 4. To this end the levers 18 carry cam rollers 2O at 'theirlower'ends journaled on pins 21 fixed to the levers, these rollers" being engaged simultaneously by a double cani 22 carried'by the drive yshaft 2 at the end of the forming' movement.

lInthe operation of the machine a'sheet S i Y is laid'l upon thefixed form la immediately pivoted forming members 6 engage with the I sheet along the bending linesm and during the first portion of. the downward movement the rollers 11 travel along the vertical guides 1b so that' the forms 6 movestraight down until thefsheet S is brought into engagement with theupper edge Aof thev rib 4 of the fixed form. During this initialV movement the sheet S is bent slightly about the lines m, since the upper Vedge of the rib 4 is below the opposite edges of the form la, the sliding member' 5 during this initial movement following the sheet-by gravity. The parts will now be broughtA to the positions indi-` cated inlig. 5 of the drawing in' which the sheet S restsupon opposite edge portions of the form and' upon the top edge of the vcentral-'rib thereof. In this position the rollers 11 ofthe pivotedforming niembersf are at the upper yends of the cam portionsV 18a` of the leverslS and the eccentrics 17- are in a positionf'to, begin to exert a downward rpressure uponthe hooks 16 and lthrough the; hooks 16 upon the sliding forming member 5. -Th-e sliding'member has a concavity along its bottom conforming in shapeto the shape of the peakof the rib 4 of the fixed forni.

Downward AVmovement of the sliding form 5 serves to bend the sheet S over the top Aof the ribg4 to the shape of the upper edgev of the rib 4. The cams A18a have a curvature such that .during the' downward movement of the side edges of the sheet.

ly toward the position shown in Fig. 1 of the drawings, the sheet S is bent simultaneously along the two lines m and .along the line n midway between the lines m. The cam surfaces 18a do not guide the pivoted members tothe full extent of their inward movement for the reason that as the rollers 11 approach their lowest positions, the cam surfaces 18a get so flat as to practically lock 'the downward movement. To overcome this difficulty, the rollers 11, as the members 6 approach the end of their downward movement roll off the surfaces 18a onto surfaces 18?) andl atthe same instant, the doubleV cams 22. come ino engagement with the rollers 2O at thelower ends of the levers 18 pushing` the rollers 20 outwardly and swinging the levers 18 inwardly aboutv their pivots to exert a direct thrust against the outer sides of the rollers 11 pushing the pivoted members 6 inwardly about their pivot to com iress the sheet between the base portions of the ribs 4 and againstfthe form 1a adjacent the bends. During these final movements, the main links 13, the eccentrics 17 and the double cams l22 are ali turned into approximately dead center positions so that very heavy pressures are applied in the proper directions to give the metal the set that is necessary at the bends. To accommodate the indented holes 3 in the body of the sheet,

those portions of the form which would otherwise engage and exert pressure on the perforated areas are recessed or depressed,

vtations lie during the forming operation and prevent any pressure being exerted upon the perforated portions of the sheet which would tend to flatten -or iron out the indentations, the forming pressure being exerted upon the sheet onlyalong the unperforated strips where the lines of bend occur and along the 1f desired, fianges may be turned up along the edges'of the sheet at the portions thereof which form the side walls of the baffle and such flanges will lie outside of the forming members 6 and will not be distorted during the forming operation.

On continued movement of the drive shaft` 2 from the position shown in F ig. 1 of the drawings, the eccentrics L1'? will turn off of the hook links 16, thus freeing these links. At the same time cam faces 5a made a part of, the arms 15 will engage rollers 23 carried by pins 24 secured to the links 16, pushing these links over against stops 1cV projecting out from the main frame thus freeing the hook 16 from the eccentric 17 so that itwill clear the eccentric during its upward movement. Further turning of the arm 15 will raise the roller 23 until it rests upon a circular engaging poreV tion 15?) so that the hoolris free to be raised. Atthe same time the double cam moves out of-engagement with the rollers 20, freeing the llevers 18 and allowing the pivoted forming members 6 to open under the actionV of the springslO. All parts are now released andA the crank arm 15 acting upon the links 13 will fraise the upper shaft 7 carrying the' pivoted forming members 6 to their uppermost position, at the same time raising the sliding form '5 through the straps 9. `lhen the movable parts have been raised to their uppermostV positions, the roller 23 will be out Yof contact-with the camon the arm 15 so that the hook links will swing by gravity to vertical position ready to be again engaged li by the eccentrics 17.V

A Having described my invention, I claim- The method of forming perforated sheet metal articles which'have portions withrela-V tively sharp bends, which comprises-perforating'a sheet to provide perforated areas with relatively narrow unperforated strips lyingbetween the perforated areas and subjecting the sheets to pressure between forming members engaging Vthe sheets along the Vunperforated strips only.

-K V2. The method f forming perforated sheet metal articles having relatively sharp bends Y which comprises perforating the major por- Y 'tion ofa flat sheet leavingunperforated a- "strip along a line ofvbend andalcng the edges ofthe sheet,'bendingthe sheet along the unperforated portion, holding the unperforated vedgesofthe sheet thereof against angularly disposed walls of va form conforming to a portion of the article being formed and ap' plying pressure to thelunperforated portions of the sheet to give the metal a permanent set to the shape of the form.

3.7The method of forming sheet Vmetal articlesfhavingV relatively sharpA bends and flanged perforations in the body thereof,

whichjcomprises forming flanged yperfora-L tions throughout the sheet except in strips along the edges and along lines of bend, bend- A' ing said sheet vto the shape of the article beonly of the sheet.

rated strips.

ing formedbetween'forming members engaging the sheet along the unperfo-rated portions 4. The method of forming a-ribbed perforated sheet metal article havingl closely spaced perforations, which comprises forming closely spaced perforations throughout all of a flat sheet'except along narrow strips at the'edgesand along lines where the bends` at the bases and peaks of the ribs occur, .and

forming the article by subj ecting'the sheet to pressure between forming members which engage with the sheet onlyalong the 'unperfo- '5. The method Vof formingra ribbed sheet metal article having'iclosely spaced Hanged perforations which comprises forming closely Y spaced flanged perforations. throughouty the body of a flat sheet `leaving unperforated strips along the edges and-along lines where the bends at thebases andV peaks of the ribs occur, andfoiming the ribs and'intermediateV body portions of the article'by subjectingthe unperforated portions of the sheet to pressure between forming members.

6, v'Ihemethod of forming a Vribbed sheet metal cylinder having closely spaced flanged perforations, which comprises forming closely spaced flanged perforations thro'ughout the entire body of aflat sheet except along narrow strips at the edges Vand along lines where the bends at the basesfand peaks of the ribs occur, and formingV the ribs and intermediate' cylindrical body portions-of the cylinder by subjecting the sheet to pressure between forming members engaging only the unperforated strips of the sheet.

7. rlhe method-of forminga lsheet metal cylinder having integral reentrant portions from a substantially liatpiece' of sheet metal which comprises subjecting successive sections yof the sheet successively toa bending operation in which a portion yof the section acted upon is bent to form the reentrant portion and the remainder thereof is bent to ycylindrical form. 7

8. The method of forming a'sheet metal cylinder having integral reentrant portions extending longitudinally thereof fromasub-` i bending the sheetby Aapplyingpressure between bending formersr'to the unperforated strips whileholding they perforated portions between members conforming .tofthe inner and outer surfaces of the cylinder.V

Y 10. The method of `forming a sheet metal cylinder Vwith Vintegral reentrantVV portions forming baiiles which comprises bending said sheet over a form which hasa longitudinally extending rib conforming to theV outer surface of the .reentrant bafflev portion of the cylinder and a cylindrical portion at oneside of the rib simultaneously bending the 'sheet with relatively light pressure over-thefedge of the rib and along a parallel linewhich ,when thesheet is folded against ther-face of the rib willlie at theV basethereof. and finally applying heavy pressure*V upon' the sheet simultaneously` 'against theupper edgev of Sill the Vrib, :against the side-face of the rib adjacent the base thereof.

f1.1., The method of forming a sheet metal cylinder having integral reentrant4 portions and closely spaced I'i'anged perforations in both, the cylindrical body port-ion and the {reentrant portionsyWhichA comprises forming flanged perforationsin a flat sheet leaving strips imperforated along the edges and along the lines of bendinftliejportions of the sheet from which the reeiitrant portions are of the sheet at the bends to heavy pressurer between formingmelibers and at the same time forming the intermediate perforated `portions by pressing the edge portions thereof between forming members.

l2. The method of forming ribbed sheet metal articles having perforations in the body portions and in the ribsthereof which comprises forming perforations in a flat sheet leaving strips unperforated along the edges and along the lines of bend in the portions of the sheet from Which the ribs are formed, bending the sheet by clamping the same along the line of bend lying at the peak of a rib, engaging the sheet along the lines of bend lying at the base of the ribs, restraining the movement of the portion of the sheet outside the lines of bend, and applying pressure vto form the bends, andimparting a permanent set to the ribs and body portions of the Varticle by applying heavy pressure between forming members to the unperforated portions of the sheet.

13. The method of forming Vribbed sheet metal articles from flat sheets Which comprises clamping the sheet along a line of bend between forming members, engaging said sheetvvith movable forming members having a line engagement with the sheet on opposite sides of the line on Tvhicli the sheet is clamped, exerting pressure on the movable forming members to bend the sheet along the peak line of the rib, maintaining'the line engagement of the movable forming members with the same portions of the sheet during the bending movement and restraining outer portions of the sheet to `form bends along the lines yengaged by the movable formingmembers.'

14. Apparatus for forming a cylindrical ribbed shell from'sheet metal having perforated areas from which the cylindricall portions of the shell are formed and other perforated areas .from which the side Walls vof the ribs are formed and relatively narrow unperforated strips betweenl the perforated areas, which comprises pressure applying forming devices adapted to apply pressure 'l to the unperforated strips only to form relatively sharp bends tlierein to form the ribs,

and means for simultaneously bending adjacent perforated areas to cylindrical` form.

l5. Sheet metalpforming apparatus comprisingA a concave `f orm having an intermediate upstanding rib, a member co-operating therewith to clamp` a sheet upon the peak of saidrib, and a pairof sheet engaging members having edges adapted to have a line engagement with the sheet on opposite sides of the rib, each member of said pair having faces on opposite sides of its engaging `edge adaptedto conform to a side of the rib and to theconcave form, and means for moving said last mentioned members toward the base of the rib and toward opposite sides of the rib.

16. Sheet metal forming apparatus comprising a rigid concave form having an intermediate upstanding rib, and a plurality of co-operating movable formers, one of the movable foimers being adapted to clamp the sheet against the pealrof the rib of the rigid lform and other of saidformersbeingjniovable toward the rigid forni and toward opposite prising arigid form having an yintermediate upstandng rib and cylindrical face portions on opposite sides of the rib, and means cooperating W-ith said rigid form to hold the sheet against the top of the ribfand to bend the sheet over 'the rib and into conformity With the rib and cylindrical face portions ofthe rigid-form. Y j

l18. Sheet forming apparatus comprising means for clamping a sheet alonga given line, pressure applying members adaptedto engage the sheet along lines a predetermined distance from the clampingline `and to apply ,pressure to the sheet Lto bend the same about theclamping line, means for restraining the movement of the sheet to cause the .same to bend along the lines engaged by the ypressure applying members., and means for maintaining the pressure applying members V`inline engagement. Withthe sheet along the .Samelines throughout the bending movement offthefsheet; f

`19. Sheet foriningjapparatus comprising a formliavinga concave forming face and an intermediate `-rib extending out from the face, a pressure applying member movable toward and fromr the pealrjof the rib, and.a pair of pressure applying members movable toward the face of the'former and toward the'side facesof thevrib, each member of saidpair being adapted k.to-fit against thel side lof the rib and Vagainst the concave faceoffthe form at one side of the rib.

20. Sheet forming'appar-atus comprising a fornihavingV a concave face with an intermediate `projecting rib, a pressure applying membery movable :toward and from `the peak of the rib, a pair of pressure applying members having'convexs faces corresponding in AKA360,'

ies

curvature to the concave faces'of thefo'rm andv inner faces corresponding to the outer facesof the rib, and means for moving all said pressure applying members simul- 5 taneously toward the form and said pair of pressure applying members'toward the op.- `posite faces of the rib.`

21. vSheet metal forming apparatus comprising means for clamping a sheet along a ixed bending axis, pressure applying members adapted 'to engage the sheet along bending axes on opposite sides of the fixed bending axis, means for moving said pressure applying means to bend the sheet about the fixed axis and for maintaining said pressure applying members in engagement With the sheet along the bending axes during the bending movement, and means'for restraining the Y movement of portions of Ithesheet Von opposit/e sidesof the bending axes'to" cause the sheet to bend along said axes. y

" 22. Sheet metal rforming apparatus Vfor prising forming membersadaptedto engage a sheetsimultaneously along a plurality yof parallel lines, means for moving certain of said forming members relatively to other of saidfforming members and for restrainingI the movement of portions of the sheet to.

means operable at the end of the bending movement to compress the sheet at the bends. In testimony whereof, hereunto -aflix my signature. v Y j ARTHUR R. CURTIS.

Aforming ribbedk articles'comprising a set of relatively movable sheet forming members Which When brought together upon a portion of a sheet confine Ithe same to the configuration4 of a rib and vadjacent body portions of the article, saidforming members having raised marginal portions adapted to engage the sheet so confined' along the edges and along th: lines of bend at the base vand peak of the r1 f f 23.*'A sheet metal forming machine' com-V prising a fixed form, having a projecting rib,

va set of forming members movable toward and from thex'ed form, said set comprising la sliding member movabletovvardVv and from the peak of the rib, a second sliding member movable independently of said Vfirst 'mening members pivoted to saidsecond Vsliding member, and means for swinging the pivoted tioned sliding member and a pair offormforming members toward the opposite faces 'n of the rib during their movement toward the form.

24. A sheet metal'formingmachine com-V`V prising-a lixed form havingangularly dis-LV posedforming surfaces, means co-opera'ting With aportion of thegxed form to clamp a `sheet along a `bending ax'isadjacentj'an edge of one of said angularly'disposed surfaces, a

. bending member movable ltoward and-f"ro1n 'the' form, an operating shaft, meansy for operating the clamping member from the shaft,

bending member toward one ofthe angularly disposedsurfa-ces of Ithe form, a `guide lrnember-for guiding the bending Amember during its movement toward saidlast mentioned surmeans operated bythe shaftv kfor moving the fa'ceztoward'ithe other' surface'fandV a camV on 'I 'Y vthe shaft'acting on said guide memberat the end of its movement to exert'pressure thereon y to` give a permanent lset to the "metal'of the bend-. Y I v 9541A sheet metal formingmachine com- 

